The present invention relates to an optical device such as a stereo-microscope, and particularly to an optical device using a lens barrel capable of continuously varying an inclination angle of an eyepiece section, for observing an erected image.
Generally, stereo-microscopes are often used to inspect the appearance of semiconductor chips for a long period of time. At the time of the observation, if the observer continues to observe with an uncomfortable posture, the observer becomes fatigued due to stress caused in muscle, thereby making it difficult to perform the observation for a long period of time.
In order to reduce the observer's fatigue, there are proposed various kinds of lens barrels, which can arbitrarily vary the inclination angle of the eyepiece section to adjust to the observer's body and posture.
FIG. 1 shows a lens barrel disclosed in Japanese Utility Model Application KOKAI Publication No. 1-164401. As shown in FIG. 1, beams emitted from lenses 70, 70a are reflected by incident prisms 40, 40a, and made incident onto rectangular prisms 50, 50a. The beams reflected by the rectangular prisms 50, 50a are reflected by emission prisms 60, 60a, and made incident onto eyepiece casing sections 76, 76a. The beam emitted from the eyepiece casing sections 76, 76a image-form an image, which is from an object lens, on image surfaces of eyepiece sections 78, 78a.
In this case, a first rotation shaft is formed around the emission optical axes of the incident prisms 40, 40a. By means of the first rotation shaft, the rectangular prisms 50, 50a can be rotated against the incident prisms 40, 40a. Also, a second rotation shaft is formed around the emission optical axes of the rectangular prisms 50, 50a. By means of the second rotation shaft, the emission prisms 60, 60a and the eyepiece casing sections 76, 76a can be rotated against the rectangular prisms 50, 50a. The rotations of the rectangular prisms 50, 50a against the incident prisms 40, 40a and those of the emission prisms 60, 60a against the rectangular prisms 50, 50a are interlocked with each other, so that both prisms are rotated by the same angle in the same direction.
According to the above-structured lens barrel, even if the eyepiece casing sections 76, 76a are rotated, the inclination angle of the lens barrel can be continuously changed. Moreover, an object image formed on the image surface of the eyepiece sections 78, 78a by the lenses 70, 70a are reverted at their upper and lower and right and left positions by the incident prisms 40, 40a, the rectangular prisms 50, 50a, and the emission prisms 60, 60a. Then, the observing image at the eyepiece sections is an erect image.
FIG. 2 shows a lens barrel disclosed in Japanese Patent Application KOKAI Publication No. 6-175030. As shown in FIG. 2, a beam 11 from the object lens is reflected by a roof prism 8, and made incident onto an eyepiece section 9.
In this case, the eyepiece section 9 is rotated and supported such that the eyepiece section 9 can rise and fall. Then, the roof prism 8 is rotated by 1/2 of a rotation angle of the eyepiece section 9 through a synchronizing mechanism (not shown) synchronizing with the rotation of the eyepiece section 9.
According to the above-structured lens barrel, even if the inclination angle is continuously changed by the rise and fall operation of the eyepiece section 9, the beam 11 from the object lens is always guided to an eyepiece lens 10. As a result, the image position is not shifted. Moreover, the object image from the object lens is reverted at its upper and lower and right and left positions by the roof prism 8. Then, the observing image at the eyepiece section 10 is an erect image.
FIGS. 3 and 4 show a lens barrel disclosed in Japanese Patent Application KOKAI Publication No. 62-287213. As shown in FIGS. 3 and 4, a beam emitted from an image forming lens 21 is deflected by a static reflective member 22, and made incident onto a rectangular prism 23. A beam emitted from the rectangular prism 23 is reflected by the rectangular prism 23 twice. Thereafter, the beam is made incident onto a rotation mirror 24. The beam reflected by the rotation mirror 24 is guided to an eyepiece lens through a diamond-shaped prism 25.
In this case, a movable section 27 is rotated and supported by a static section 26 such that the movable section can rise and fall. An eyepiece section is supported by the movable section 27 to be rotatable round its optical axis. The diamond-shaped prism 25 is built in the eyepiece section 28. The rotation mirror 24 is supported by the static section 26 to be rotatable round the movable section 27 as a central axis. Moreover, the rotation shaft of the movable section 27 is structured to be coaxial with that of the rotation mirror 24. The rotation mirror 24 is rotated by 1/2 of the rotation angle of the movable section 27 through a linkage mechanism (not shown) in accordance with the rotation of the movable section 27.
According to the above-structured lens barrel, even if the inclination angle of the movable section 27 is continuously changed, the beam from the object lens is always guided to the eyepiece lens. As a result, the image position is not shifted. Moreover, the object image from the object lens is reverted at its upper and lower and right and left positions by the static reflective member 22, the rectangular prism 23, and the rotation mirror 24. Then, the observing image at the eyepiece section is an erect image.
The lens barrel of FIG. 1 disclosed in Japanese Utility Model Application KOKAI Publication No. 1-164401 comprises an optical element serving as both an element for erecting the image (which is essential for the stereo-microscope) and an element for varying the inclination angle of the lens barrel. There is a merit in that the number of optical elements constituting the optical device is small. However, since the rectangular prisms 50, 50a, and the emission prisms 60, 60a are relatively rotated respectively, a frame for holding each prism is needed. Due to this, it is difficult to ensure an accurate relative position of each prism.
The eyepiece casing sections 76, 76a, which are operated to change the inclination angle of the lens barrel and to adjust an eye width, is held by first and second rotation shafts. Due to this, the eyepiece casing sections 76, 76a are easily influenced by an accurate error caused in manufacturing the rotation section.
Moreover, there was a problem in that a large number of processes for adjusting the optical axis is needed.
In the lens barrel of FIG. 2, since high manufacturing accuracy for the roof prism 8 is required, the manufacturing cost is increased.
Also, because the roof prism 8 is rotated by synchronizing with the eyepiece section 9, the angle, which is formed by the optical axis and the beam incident surface of the roof prism 8, is different depending on the inclination angle of the eyepiece section 9. As a result, there was a problem in that the center of the rotation of the roof prism 8 and the reflective point of the roof prism 8 are shifted, and in that the roof prism must be formed in an afocal optical system.
Moreover, when the lens barrel of FIG. 2 is applied to a Galilean stereo-microscope, an eye width adjusting mechanism is needed. In the adjusting mechanism, each diamond prism (not shown) is provided between the eyepiece lens 10 and the roof prism 8. Then, the incident optical axes of the diamond prisms are used as rotation shafts, and the diamond prisms are rotated. Thereby, the right and left optical axes to adjusted to the observer's eye width. The Galilean stereo-microscope is a stereo-microscope, which comprises a parallel optical system having a pair of parallel optical paths formed at a back of the object lens.
However, the distance between the right and left optical axes is fixed until the beams are made incident onto the diamond prisms. In the Galilean stereo-microscope, the distance is restrained by the size of the object lens, the focal distance, and the numerical aperture. As a result, the distance is not increased, and the structure of the rotation mechanism for rotating the prisms in which the incident optical axes are rotated as rotation shafts becomes complicated. Also, there is a problem in that a visual viewing field is not enlarged by the restriction of the rotation shaft mechanism. Moreover, it is difficult to apply the lens barrel of FIG. 2 to a three-eye barrel to which an optical path for photographing is added.
In the lens barrel of FIGS. 3 and 4, the beam emitted from the image forming lens 21 is reflected toward the rectangular prism 23 by the fixed reflective member 22. In this case, the rectangular prism 23 is positioned at the eyepiece section 28. Due to this, the angle of the indecent optical axis (barrel inclination angle) to the eyepiece section 28 cannot be set to a range from 0.degree. (the horizontal) to 20.degree. against the horizontal. Such an angle range maybe suitable for a long time observation using the microscope. It can be, of course, considered that the rectangular prism 23 is retreated to the position where the setting of the suitable angle range is not prevented by the rectangular prism 23. In this case, the distance between the static reflective member 22 and the rectangular prism 23 and the distance between the rectangular prism 23 and the rotation mirror 24 are increased. As a result, the lens barrel cannot be structured in the optical path length, which is determined by the focal distance of the image forming lens 21.
Moreover, it can be considered that the beam emitted from the image forming lens 21 is reflected to be opposite to the eyepiece section 28 by the static reflective member 22. However, in this case, the angle formed by the optical axis of the emitted beam and the reflected surface of the rotation mirror 24 is extremely small. As a result, it is difficult to set the inclination angle of the lens barrel to the range from 0.degree. (the horizontal) to 20.degree. which is suitable for the long period of observation using the microscope.
Furthermore, it is difficult to apply the lens barrel of FIGS. 3 and 4 to the three-eye barrel to which the optical path for photographing is added.
In consideration of the above-mentioned problems, the present invention has been made. An object of the present invention is to provide a lens barrel, a stereo-microscope, and an optical device, which can observe a real image in a condition that an inclination angle of the barrel can be continuously varied in a range resisting a long time observing, with a simple structure and at low cost.